The present invention is related to a lens assembly, and more particularly to a lens assembly which employs an electromagnetic coil for creating magnetic force to adjust the focal length of the lens assembly.
FIG. 6 shows a conventional CCD lens assembly including a hollow lens seat 92 mounted on the CCD module 91. The lens seat 92 is formed with an inner thread section 921 in which a lens holder 93 is screwed. A lens 94 is disposed on the lens holder 93.
Such CCD lens assembly adjusts focal length by means of rotating the lens holder 93. However, the adjustment must be manually made and the adjustment range is limited. Moreover, with respect to the CCD lens assembly, it is hard to further adjust the focal length.
In the mechanical focusing mechanism of existent lens assembly, a motor via a reducing gear assembly drives the lens holder for adjusting focal length. Such structure is complicated and quite expensive so that it can be hardly widely used.
It is therefore a primary object of the present invention to provide a lens assembly. An electromagnetic coil is wound around the circumference of the lens seat. The lens holder is made of magnetic conductive material. After the coil is powered on, the coil creates a magnetic force to push and move the lens holder and change the distance between the lenses and thus adjust the focal length of the lens assembly.
It is a further object of the present invention to provide a lens assembly which is adjustable in focal length. The lens assembly has very simple structure and is manufactured at low cost.
The present invention can be best understood through the following description and accompanying drawings wherein: